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28 October 2019 | Story Leonie Bolleurs | Photo Anja Aucamp
Dr Brain van Soelen and Prof Pieter Meintjies
UFS scientists, Prof Pieter Meintjes and Dr Brian van Soelen, are part of the prestigious H.E.S.S. collaboration that recently published in Nature Astronomy.

Think of an object with a mass exceeding that of the Sun, squeezed into a volume of a sphere with the radius of a city like Bloemfontein. This very dense, compact object, known as a pulsar, is also a great source of energy. According to Physics Professor, Prof Pieter Meintjes, this pulsar (neutron star produced in supernova explosion) is also a key element of a recently submitted paper in Nature Astronomy.

Prof Meintjes and Dr Brian van Soelen, Senior Lecturer, both from the Department of Physics at the University of the Free State (UFS), were part of the High Energy Stereoscopic System (H.E.S.S.) collaboration of 220-plus scientists worldwide who worked on the paper Resolving the Crab pulsar wind nebula at tera-electronvolt energies, published in the prestige journal Nature Astronomy. 

According to Prof Meintjes, the fact that the paper was accepted for publication in Nature Astronomy testifies of the importance of this finding in the high-energy astrophysics community.

Powerful generators of electricity

He elaborates on the study: “The name pulsar originates from the fact that rotating neutron stars produced in supernova explosions produce beams of radiation, much like a lighthouse. Every time the beam intersects the observer’s line of sight, the observer receives a pulse of radiation.”

“As a result of this enormous mass squeezed into a small volume, these objects have the same density as that of an atomic nucleus. These objects (very dense pulsars) spin very rapidly and have enormous magnetic fields; for example, the pulsar at the centre of the Crab Nebulae spins around its axis once every 33 milliseconds (millisecond: one thousandth of a second) and possesses a magnetic field strength of the order of one tera-Gauss (tera – million x million). For comparison, the average strength of the Earth’s magnetic field is 0.5. Gauss and the magnetic field strength on the Sun ranges between 1 000 and 4 000 Gauss.”

“Because of this very super-strong rapid-spinning magnet, enormous electric fields are induced that can accelerate particles such as electrons and protons to energies in excess of one tera-electronvolt (optical light that are emitted by an ordinary lightbulb has energies of the order of one electronvolt).”

Prof Meintjes continues: “This means that these fast-rotating neutron stars are extraordinary powerful generators of electricity, which fills the surrounding cloud (supernova remnant) with super-high energy-charged particles that can produce, in turn, very high energy gamma rays through various processes such as synchrotron radiation and inverse-Compton radiation, to name a few.”

H.E.S.S. collaboration 

Above one tera-electronvolt, the gamma rays are detected by huge ground-based telescopes such as H.E.S.S., utilising the Earth’s atmosphere.

“When these high-energy gamma rays enter the atmosphere, they produce showers of super-relativistic particles that produce Cherenkov light – detected by the telescope. The technique is called the Atmospheric Cherenkov Technique (ACT).”

HESS
The High Energy Stereoscopic System. (Photo: Supplied)

“The H.E.S.S. gamma-ray collaboration is but one collaboration that has studied this source intensively over the past couple of decades or so.  Being the most powerful gamma-ray telescope facility currently operational, very careful analysis of the data managed to reveal that the gamma-ray emitting region inside the nebula is about 10 times bigger in size than the region where the x-rays are emitted within the nebula.” 

“This has solved a long-standing question as to how big the gamma-ray emitting region within these supernova remnants are, compared to the region where the x-rays, for example, originates,” says Prof Meintjes. 

Both Prof Meintjes and Dr Van Soelen are members of this prestigious H.E.S.S. collaboration. Their participation in this project, together with scientists from universities such as the University of Oxford, the University of Leicester, and the University of Bordeaux, opens up valuable research opportunities for UFS postgraduate students to enter the international stage and interact with the best scientists in the world.

They are also members of the editorial board responsible for the internal review of research papers before being submitted to more prestigious journals, for example, Nature Astronomy. Dr Van Soelen is also a coordinator of multi-wavelength follow-up observations within the H.E.S.S. collaboration. 

This is the second time that Prof Meintjes published in Nature Astronomy. Previously, he was co-author of a paper on emission from a white dwarf pulsar, showing that fast-rotating white dwarf stars could in fact mimic emission from neutron star pulsars. He developed the theoretical model reported in that paper, explaining the multi-wavelength emission from radio to X-ray energies.


News Archive

Position statement: Recent reporting in newspapers
2014-10-03

 

You may have read reports in two Afrikaans newspapers, regarding recent events at the University of the Free State (UFS). Sadly, those reports are inaccurate, one-sided, exaggerated and based not on facts, but on rumour, gossip and unusually personal attacks on members of the university management.

Anyone who spends 10 minutes on our Bloemfontein Campus would wonder what the so-called ‘crisis’ is about.

We are left with no choice other than to consider legal action, as well as the intervention of the South African Press Ombudsman, among other steps, to protect the good name of the institution and the reputation of its staff. No journalist has the right to launch personal and damaging attacks on a university and its personnel, whatever his or her motives, without being fair and factual. In this respect, the newspapers have a case to answer.

But here are the facts in relation to the reports:

  1. No staff member, whether junior or senior, is ever suspended without hard evidence in hand. Such actions are rare, and when done, are preceded by careful reviews of our Human Resource Policies, labour legislation and both internal and external legal advice. Then, and only then, is a suspension affected. A suspension, moreover, does not mean you are guilty and is a precautionary action to allow for the disciplinary investigation and process to be conducted, especially where there is a serious case to answer.
  2. At no stage was the Registrar instructed to leave the university; this is patently false and yet reported as fact. We specifically responded to the media that the Registrar does outstanding work for the university and that it is our intention for him to remain as our Registrar through the end of his contract in 2016.
  3. The Rector does not make decisions by himself. Senior persons, from the position of Dean, upwards, are appointed by statutory and other senior committees of the university and finally approved by Council. No rector can override the decision of a senior committee, and this has not happened at the UFS even in cases where the Rector serves as Chair of that committee. The impression of heavy-handed management at the top insults all our committee structures, including the Institutional Forum – the widest and most inclusive of stakeholder bodies at a university – which reports directly to Council on fairness and compliance of selection processes.
  4. In the case of senior appointments, Council makes the final decision. Council fully supports the actions taken on senior appointments, including a recent senior suspension. The fact that one Council member resigns just before the end of his term, whatever the real reason for this action, does not deter from the fact that the full Council in its last sitting approved the major staffing decisions brought before it. The image therefore that the two newspapers try to create of great turmoil and distress at the university, is completely unfounded.

Even if we wanted to, the university obviously cannot provide details about staffing decisions, especially disciplinary actions in process, since the rights of individuals should be protected in terms of the Human Resource Policies and procedures of the UFS. But that does not give any newspaper the right to speculate or state as fact that which is based on rumour or gossip, or to slander senior personnel of the university. For these reasons, we have been forced to seek legal remedy and correction as a matter of urgency.

Make no mistake, underlying much of the criticism of the university has been a distress about transformation at the UFS; in particular, the perception is created that white colleagues are losing their jobs. The evidence points in the opposite direction. Our progress with equity has been slow and we lag far behind most of the former white universities; that is a fact. More than 90% of our professors are white; most of our senior appointments at professorial level and as heads of department are still overwhelmingly white. Reasonable South Africans would agree that our transformation still has a long way to go and only the mean-spirited would contend otherwise. But based on the two Afrikaans newspaper reports, an impression is left of the aggressive rooting out of white colleagues.

In the past few years the academic standard of the university has significantly improved. We now have the highest academic pass rates in years, in part because we raised the academic standards for admission four years ago. We now have the highest rate of research publications, and among the highest national publication rate of scholarly books, in the history of the UFS. We have one of the most stable financial situations of any university in South Africa, with a strong balance sheet and growing financial reserves way beyond what we had before. We now attract top professors from around the country and other parts of the world, and we have the highest number of rated researchers, through the National Research Foundation, than ever before. And after the constant turmoil of a number of years ago, we now have one of the most stable campuses in South Africa. Those are the facts.

The UFS is also regarded around the world as a university that has become a model of transformation and reconciliation in the student body. The elections of our Student Representative Council are only the most visible example of how far we have come in our leadership diversity. Not a week goes by in which other universities, nationally and abroad, do not come to Kovsies to consult with us on how they can learn from us and deepen their own transformations, especially among students.

Rather than focus on what more than one senior journalist, in reference to the article in Rapport of 21 September 2014, rightly called ‘a hatchet job’ on persons and the university, here are the objective findings of a recent survey of UFS stakeholders: 92% endorse our values; 77% agree with our transformation; 78% believe we are inclusive; and 78% applaud our overall reputation index.  Those are very different numbers from a few years ago when the institution was in crisis.

This is our commitment to all our stakeholders: we will continue our model of inclusive transformation which provides opportunities for study and for employment for all South Africans, including international students and colleagues. We remain committed to our parallel-medium instruction in which Afrikaans remains a language of instruction; we are in fact the only medical school in the country that offers dual education and training in both Afrikaans and English for our students - not only English. We provide bursaries and overseas study opportunities to all our students, irrespective of race. And our ‘future professors’ programme is richly diverse as we seek the academic stars of the future.

We are not perfect as a university management or community. Where we make mistakes, we acknowledge them and try to do better the next time round. But we remain steadfast in our goal of making the UFS a top world university in its academic ambitions and its human commitments.

END

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